The present invention relates to a method for bending and tempering a glass sheet, in which method a glass sheet is heated in a furnace station close to a bending temperature, the heated glass sheet is carried into a positioning and bending station, wherein the glass sheet is supported by the pressure of an underneath gas bed and the glass sheet is positioned relative to a gas-bed surrounding ring mould by bringing the leading edge of a glass sheet gliding on the gas bed to collide with a positioning abutment and by lifting up a positioning abutment for the trailing edge and/or side edges the glass sheet is partially or completely laid to be supported by the ring mould, the glass sheet is heated and allowed to bend gravitationally close to a final bending shape.
The invention relates also to an apparatus for bending and tempering a glass sheet, comprising a preheating furnace, a positioning and bending station and a quenching station, the positioning and bending station including a glass-sheet supporting gas bed, a gas-bed surrounding ring mould which is reciprocable in vertical direction, and positioning elements for positioning the gas-bed supported glass sheet relative to the ring mould.
This type of method and apparatus are known e.g. from U.S. Pat. Nos. 3,468,645; 3,607,200; 3,846,104; 3,869,271; 4,229,200 and 4,432,782, which are briefly referred to in U.S. Pat. No. 4,612,031.
An object of the present invention is to further develop this type of method and apparatus in view of further improving the achievement of the following objectives:
1. Strict profile tolerances (particularly at glass sheet edges) PA0 2. Acceptable optics despite sufficient heating for proper tempering PA0 3. Sufficient capacity PA0 4. Flexible, a glass-type replacement time about half a working day.
Thus, the invention seeks to provide a solution, whereby a glass sheet made a homothermal as possible is capable of bending all the way to the edges and corners and then capable of retaining the glass shape or profile during the course of heating and transfer to tempering in an accurately bent form.
These objects of the invention are achieved on the basis of inventive characterizing features set forth in the annexed claims.